FormatDrop
Document Format

ICS

iCalendar

ICS (iCalendar) is the universal calendar file format used by Google Calendar, Apple Calendar, Outlook, and every modern calendaring system. Defined in RFC 5545, iCalendar standardized how calendar events are exchanged between systems. ICS files contain one or more events with full metadata — start/end times, time zones, recurrence rules, attendees, alarms, and rich descriptions.

What is ICS?

ICS files are plain text following a structured format. The file starts with BEGIN:VCALENDAR, contains VEVENT blocks (one per event), and ends with END:VCALENDAR. Each VEVENT specifies SUMMARY (title), DTSTART/DTEND (start/end with time zone), DESCRIPTION, LOCATION, ORGANIZER, ATTENDEE, RRULE (recurrence rule), and VALARM (notification). Time zones are encoded as TZID references to embedded VTIMEZONE definitions.

ICS pros and cons

Advantages

  • Universal format — every calendar app reads it natively
  • Rich event metadata (recurrence, attendees, alarms, time zones)
  • Plain text — readable and editable in any text editor
  • Round-trip safe between Google Calendar, Apple, Outlook, and Office 365
  • Supports multiple events per file (export entire calendars)

Limitations

  • Time zone handling is complex and inconsistently implemented across apps
  • Recurring events with exceptions can be tricky to edit
  • No standard for tasks (some apps include VTODO; many don't support it)
  • Bulk editing requires text manipulation or conversion to CSV

When should you convert ICS files?

Convert ICS to CSV for bulk analysis in Excel — meeting hours per attendee, time zone audits, etc. Use Python's icalendar library or online tools. Convert CSV to ICS for bulk-creating events from a spreadsheet (e.g., creating a conference schedule from a session list).

Convert ICS files

DOCUMENT-CONVERTER→

All FormatDrop conversions run entirely in your browser — no file upload, no server processing. Your files stay on your device.

ICS FAQ

How do I import an ICS file into Google Calendar?
calendar.google.com → Settings → Import & Export → Import → choose your .ics file → select target calendar → Import. All events appear with full metadata. Recurring events expand correctly, attendees are imported, time zones are preserved.
Can I share an ICS subscription URL?
Yes — calendaring apps support 'subscribed' (read-only) calendars via webcal:// or https:// URLs pointing to ICS files. Apple Calendar: File → New Calendar Subscription. Google Calendar: Add calendar → From URL. The calendar updates as the source ICS changes.
Why are some events missing time zones in my ICS?
All-day events typically don't include time zones (they're date-only). Some older calendar systems export events without TZID, defaulting to floating time (interpreted in the recipient's local time zone). Modern iCalendar best practice always includes TZID for timed events.

More formats

HEICWebPAVIFEPUBWebMOpusMP3WAVM4AFLACAACMP4AVIMKVMOVJPGPNGGIFSVGTIFFICOBMPEPSARWOGGWMVPPTXPagesPDFDOCXRAWHEVCH.264AIFFM4VWMA3GPDNGRTFPSDOGVTSFLVAIXLSXCSVZIPAPNGMIDIJPEG XLMPG/MPEGVOBM2TSAC3ALACDTSJP2HEIFAPECBZ3G2SRTDOCPPTXLSODTODSM3URAR7ZM4BAMRTXTMOBITARGZJSONXMLYAMLKEYMTSCR2NEFMXFTGACAFASSVTTDSFRMF4VWVASFRMVBORFRW2EAC-3TTAISODMGXZDjVuFB2AUM4RAZW3MKAEXRVCFAAXPRCMP2SPXXSPFM3U8